Multidimensional analysis of Drosophila wing variation in Evolution Canyon

Heat-shock protein 90 (Hsp90) chaperones the maturation of many regulatory proteins and, in the fruitfly Drosophila melanogaster, buffers genetic variation in morphogenetic pathways. Levels and patterns of genetic variation differ greatly between obligatorily outbreeding species such as fruitflies and self-fertilizing species such as the plant Arabidopsis thaliana. Also, plant development is more plastic, being coupled to environmental cues. Here we report that, in Arabidopsis accessions and recombinant inbred lines, reducing Hsp90 function produces an array of morphological phenotypes, which are dependent on underlying genetic variation. The strength and breadth of Hsp90's effects on the buffering and release of genetic variation suggests it may have an impact on evolutionary processes. We also show that Hsp90 influences morphogenetic responses to environmental cues and buffers normal development from destabilizing effects of stochastic processes. Manipulating Hsp90's buffering capacity offers a tool for harnessing cryptic genetic variation and for elucidating the interplay between genotypes, environments and stochastic events in the determination of phenotype.

Genetic variability in quantitative traits can change as a direct response to the environmental conditions in which they are expressed. Consequently, similar selection in different environments might not be equally effective in leading to adaptation. Several hypotheses, including recent ones that focus on the historical impact of selection on populations, predict that the expression of genetic variation will increase in unfavourable conditions. However, other hypotheses lead to the opposite prediction. Although a consensus is unlikely, recent Drosophila and bird studies suggest consistent trends for morphological traits under particular conditions.